When applied with amine-based curing agent such as polyamine and polyamidepolyamine under low temperature and high humidity, epoxy resin paint has remarkable problems such as the inhibition of adhesion of top coating caused by amine blushing and the blushing of coating film. In order to overcome these problems, it has been proposed to improve amine-based curing agent or to improve epoxy resin.
In connection with the improvement of amine-based curing agent, Official Gazette of Japanese Patent Application KOKAI Publication No. H09-202821 discloses that curing agent which is obtained from a Mannich reaction of (A) a hydroxy aromatic compound modified with an aromatic hydrocarbon formaldehyde resin, (B) a polyamine, and (C) an aldehyde has a comparatively low viscosity and excellent hydrophobicity and allows neither amine blushing nor insufficient crosslinking to occur.
In connection with the improvement of epoxy resin, Official Gazette of Japanese Patent Application KOKAI Publication No. S58-109567 discloses that a corrosion-resistant paint composition which comprises as essential components a liquid polyhydric phenol glycidyl ether type epoxy resin (A) which is a reaction product obtained by the reaction of a monohydric phenol with a reaction product of a polyhydric phenol and epichlorohydrin or by the simultaneous reaction of a polyhydric phenol, a monohydric phenol and epichlorohydrin, wherein monohydric phenol in each of the above-mentioned reactions accounts for 3-15% by weight of the whole reaction products, an amino compound (B) which contains at least two active hydrogen atoms per molecule, and a rust-inhibiting pigment (C) exhibits a very high curing rate, and hardly causes amine blushing.